Acute Preoperative Hemodilution Research Articles

Acute preoperative hemodilution in patients undergoing radical prostatectomy: A case study analysis of efficacy.

Acute preoperative hemodilution in patients undergoing radical prostatectomy: A case study analysis of efficacy.

Acute Preoperative Hemodilution in Patients Undergoing Radical Prostatectomy

Despite published guideline and consensus conference recommendations, the role of acute preoperative hemodilution in elective surgery has not been defined. We performed a case study analysis of this technique in a large surgical program in order to estimate its degree of efficacy as practiced routinely, and to better define its role as a blood conservation strategy. Patients undergoing elective radical prostatectomy by one surgeon during a 3-yr period were analyzed retrospectively for blood loss, hematocrit levels, records of acute hemodilution, and transfusion outcomes. Patient blood volumes were determined by nomogram; final hematocrits after discrete blood volumes lost by surgery or by hemodilution were estimated. Sixteen (4.4%) of 410 total patients reviewed underwent hemodilution, representing 0 (0%), 4 (3%), and 12 (8%) of the 112, 146, and 152 patients undergoing surgery in years 1, 2, and 3, respectively. Median whole blood volume and mean red blood cell (RBC) volume removed by hemodilution was 1000 mL (range, 400-1500 mL) and 338 mL (range, 156-585 mL), respectively, representing 15% of patients' admission RBC volume. Net intraoperative RBC volume "saved" in losses by this technique was 95 mL (range, 25-204 mL), representing only 9.3% (range, 4%-17%) of total RBC volume lost during hospitalization. RBC volume removed by hemodilution constituted 34% (95-283 mL) of the total RBC volume transfused. We conclude that use of acute preoperative hemodilution remains in evolution and, as a single blood conservation intervention, contributes only modestly to blood conservation.

Blood Conservation and Blood Salvage

Autologus blood transfusion has been recommended as the blood of choice for surgical patients. Procurement of autologus blood can be accomplished by utilizing one or more conservation interventions: preoperative autologous blood donation, acute preoperative hemodilution, and perioperative autologous salvage. Recent estimates of cost-effectiveness emphasize that blood conservation interventions need to be held accountable with regards to their costs as well as their benefits. Despite recent advances in blood safety, patients need to be informed of the relative risks of blood transfusion and blood conservation, so that a careful balance of the need for blood conservation along with an acknowledgment of the life-saving properties of blood can be maintained.

Acute preoperative hemodilution in cardiac surgery: Volume replacement with a hypertonic saline-hydroxyethyl starch solution

Preoperative hemodilution (HD) is a recommended practice in cardiac surgery that conserves blood and reduces the complications of homologous blood transfusion. In 45 patients undergoing myocardial revascularization, HD was performed preoperatively. Withdrawn volume (10 mL/kg) was replaced either by a new hypertonic saline (HS) solution prepared in hydroxyethyl starch (HES) (2,400 mOsm/L, HS-HES group, n = 15) or by a standard low molecular weight hydroxyethyl starch solution (6% HES 200/0.5, HES group, n = 15) to maintain baseline PCWP (acute normovolemic hemodilution [ANH]). Fifteen comparable patients without HD served as controls. Significantly less HS-HES (210 ± 20 mL) than HES 6% (890 ± 90 mL) was necessary to sustain hemodynamics during HD. Stable cardiocirculatory conditions were obtained even after termination of bypass. Fluid balance during cardiopulmonary bypass as well as in the postoperative period was significantly lower in HS-HES-treated patients. With regard to hemodynamics, CI increased most in the HS-HES group (+36%), whereas systemic vascular resistance was lower in these patients. Right ventricular ejection fraction increased only in HS-HES patients (+15%). However, sodium concentration as well as osmolarity increased after volume replacement with HS-HES, without exceeding normal values. None of the patients suffered from organ failure. Pulmonary gas exchange (Pa0 2) was less compromised in the HS-HES patients. There were no renal function differences between the groups. In conclusion, HS solution prepared in HES is an attractive alternative for blood substitution in cardiac patients undergoing acute hemodilution for blood conservation.

Primary Hemostasis in Hemodilution -1) Hematocrit

There are still controversies about the influence of acute preoperative hemodilution on coagulation. Therefore, we examined the platelet function by the In-vitro bleeding test (IVBT) using composed blood samples of different hematocrit but constant platelet concentration. We found an inverse correlation between hematocrit and bleeding time (p less than .05), volume (p less than .001) and flow (p less than .001). These data suggest a considerable impairment of primary hemostasis, due to low hematocrit. The cause may be an alteration of the hemorheology as well as the interaction between red cells and platelets themselves.

Hemodilution

The dilution of whole blood leads to a significant improvement of its rheologic properties based on a decrease in hematocrit and, hence, blood viscosity. Under conditions of normovolemia and an adequate response of the cardiorespiratory system, the acute dilution of blood will enhance the venous return to the heart and thereby improve total and capillary blood flow significantly. In the hematocrit range of 25 to 30 per cent (limited hemodilution), this increase in flow rate is able to compensate fully for the diminished oxygen content of the blood. Changes in oxygen extraction or in oxygenhemoglobin affinity are only encountered at hematocrits below 20 per cent or if hemodilution is associated with hypovolemia. Since normovolemia is the condition sine qua non for the heart to increase its output compensatorily, intentional hemodilution should preferably be performed with colloid solutions which are capable of maintaining the colloid osmotic pressure of plasma and the circulating volume in normal limits. Limited normovolemic hemodilution with its beneficial effects on microcirculatory flow and tissue nutrition is emphasized for the treatment of impaired microcirculation as occurring in shock and low flow states, polycythemia, and high viscosity syndromes. Acute preoperative hemodilution is a means of reducing the use of bank blood and of avoiding the risks of blld transfusions in patients undergoing major elective surgery. Extreme hemodilution and total body washout in hypothermia appear to be effective clinical tools.

Acute preoperative hemodilution patients.

Acute preoperative hemodilution patients.

Acute preoperative hemodilution in surgical patients.

Acute preoperative hemodilution in surgical patients.